This disclosure relates to roll forming, pattern rolling machines that employ symmetrical, reciprocating dies. It further relates to mechanism that imparts the pattern upon an otherwise unsupported blank captured between the die faces.
Cold forming of a thread, gear tooth or other pattern upon a cylindrical blank utilizing reciprocating, symmetrical dies represents known technology. Examples are found in U.S. Pat. Nos. 387,184; 3,793,866 and 4,712,410. Such machines have not achieved any significant long-term commercial success. Some are complex and cumbersome.
Machine screws with rolled threads are widely used in industry. They are typically formed using known flat die technology in existence for many years. The commonly used flat rolling dies include a stationary (short) die on a stationary platen and a reciprocating (long) die on a reciprocating slide arranged in face-to-face relation. The machine drive advances the moving die to create the thread form. Though reliable, these machines require experienced operators to setup and run. The thread rolling machines most commonly used today represent technology developed long ago, with heavy metal components subject to wear and often requiring expensive repairs.
Moreover, the foregoing thread rolling machines include an insertion finger that positions a blank between the die faces such that advancement of the moving die captures the blank for linear movement through the die faces to impart the thread form. Synchronization of the thread forming patterns on the die faces with initial insertion of the blank between the faces is a critical aspect of thread forming. The machines employed include various adjustment elements to permit refinement of these critical relationships.
The mechanism of the insertion finger represents a major element of the current thread forming equipment. Machine maintenance, as well as repair and replacement of these components adds considerably to the overall cost of commercial fastener manufacturing.
The present disclosure is directed to cold forming equipment of advanced design utilizing aspects of currently available technology, such as servo-motors, belt drives, light weight slides operating on re-circulating bearings and symmetrical, reciprocating dies. Implementation of the disclosed equipment should revolutionize cold forming of threaded fasteners and other similarly manufactured cylindrical, patterned products.